Lorentz Symmetry

"Imagine you are about to create a universe. How would you do it? As soon as you say "let there be the laws of physics" you would immediately face a problem. Do the same laws hold for everyone in your universe regardless of where they are? Or do the laws change as you move about or face in different directions? Clearly the most equitable and fair way to proceed would be to make the laws of physics the same for all observers. To a physicist such equality and fairness of physical laws is called a symmetry, and the symmetry that requires the laws of physics to be the same for all observers is known as Lorentz symmetry."

"Symmetry is one of the most important concepts in physics, and it is closely linked to the conservation of quantities such as energy, momentum and charge. However, symmetry breaking is also incredibly important. The breaking of electroweak symmetry, for example, is responsible for the generation of mass in the Standard Model of particle physics." 01-06

"The idea of Coleman and Glashow is the following. Suppose that Lorentz symmetry is not a true symmetry of nature. This opens up the possibility that the limiting speeds (the highest speed which can be attained) of different particles, are different from each other. Suppose in particular that the speed of light (of electromagnetic radiation) and the limiting speed of a proton were not the same, and that the speed of a proton were higher. Then it turns out that the proton would lose energy to electromagnetic radiation, until its speed was the same as the speed of light."

"The way this works is the following. Since the proton is electrically charged, it carries around an electromagnetic field. When the proton moves, the electromagnetic field of the proton must move with it. The emission of electromagnetic radiation (light) can be understood as that electromagnetic field continuing to propagate, when the proton's motion is changed by some external force; so every time a proton changes its speed or direction of motion, some of the electromagnetic field accompanying it continues in the old direction and becomes radiation. If a proton were moving faster than the speed of light, then it would 'outrun' its own electromagnetic field; without any acceleration being necessary, the electromagnetic field of the proton would get stripped away from the proton and propagate away as photons (electromagnetic radiation). Since the proton is charged, it would continuously regenerate electromagnetic field; but this field would continuously fall behind the proton and be lost as radiation, until the proton slowed down to the speed of light, whereupon the electromagnetic field could keep up with it. This is what happens when a medium, such as water, a crystal, or the air, modifies the speed that light travels; charged particles which travel faster radiate 'Cherenkov' light." 01-06